RE: SPRINKLER LOAD[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: SPRINKLER LOAD
- From: "Garner, Robert" <rgarner(--nospam--at)moffattnichol.com>
- Date: Fri, 24 Jun 2005 10:20:13 -0700
I recall a metal building with an 8" diameter sprinkler main in the upper part of the building. A fire inspector was testing the main shut-off valve located just outside the building. The yoke of the valve broke off and the valve instantly slammed shut. The resulting water hammer caused the 8" main to literally shoot out the end of the building, dragging half of the laterals with it. The main was about 50 feet from the building.
From: Hans E Boge
Another issue to consider is thrust bracing where mains and feeder lines do 90 degree turns either vertically and horizontally. These thrust forces can be 2-5kips in range depending on the hydraulics of the system. These forces are high in the basements where the pumps are typically located. There are vertical gravity and thrust hangers to keep the pipe from galloping, but thrust bracing is typically vertical bracing at 45 degrees with 2 pieces. The direction of flow matters when you lay these bracing systems out. Hopefully there is some concrete deck available to handle the lateral loads. Dry systems are especially bad – water hammer; charged systems are a little better. Also watch out for code requirements in seismic areas. Fire is a common secondary effect after the shockwaves, so they want the sprinkler systems operational to minimize the damage. They may require more frequent spacing of vertical and thrust bracing than what calculation show.
Boge Boge (1980) Ltd.
Hans E. Boge, P. Eng.
p:(204) 942-7276 ext 223
When I worked in the metal building industry, we almost always used 3 psf collateral load. The relatively small piping for typical runs can be covered by 1 psf, but when you get to the larger trunk lines, 3 psf is sometimes not enough. And for the larger lines, individual attachment points can have very larges applied loads (large as in several hundred pounds), so I typically assume a sprinkler load for design, then back-check the framing once the final sprinkler layout is determined. 3 psf is probably a good starting point, but you need to consider the specific situation.
WHAT'S A GOOD PSF VALUE TO USE SPRINKLERS? NOTE TYPE V 1 HOUR.
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